Thousands marched in Manila to vent their anger over a ballooning scandal involving bogus flood-control projects believed to have cost taxpayers billions of dollars.

Rage over the so-called “ghost infrastructure” projects has been mounting in the Southeast Asian country since President Ferdinand Marcos Jr put them centre stage in a July State of the Nation address that followed weeks of deadly flooding.

Marcos said last week that he did not blame people for protesting “one bit”, while calling for demonstrations to remain peaceful.

Sunday’s protests were largely peaceful, with small groups of mostly young men throwing rocks and bottles at police, and setting fire to the tyres of a trailer used as a barricade near a bridge leading to the presidential palace.

According to the AFP news agency, some police picked up rocks and threw them back at demonstrators.

Police advancing behind a wall of shields arrested 17, mostly young, people in one encounter, local authorities said.

Barely an hour later, a second clash saw police use water cannon on another group of masked protesters.

It was not immediately clear if those involved had any connection to the organised protests.

The day began with a peaceful morning protest in the capital’s Luneta Park that drew nearly 50,000 people, according to city estimates.

Thousands more joined an afternoon demonstration at the capital’s EDSA (Epifanio de los Santos Avenue) thoroughfare, ground zero for the 1986 movement that ousted Marcos’s dictator father.

Teddy Casino, 56, chairman of the left-wing alliance Bagong Alyansang Makabayan, said the group was demanding not only the return of stolen funds but also prison time for those involved.

The Department of Finance has estimated that the Philippine economy lost up to 118.5 billion pesos ($2bn) from 2023 to 2025 due to corruption in flood-control projects.

Greenpeace has suggested the number is actually closer to $18bn.

Earlier this month, the owners of a construction firm accused nearly 30 House members and Department of Public Works and Highways officials of taking cash payments.

The scandal has already led to leadership changes in both houses of Congress, with House Speaker Martin Romualdez, a cousin of Marcos, tendering his resignation earlier this week as an investigation got under way.